Effect of a telluric correction using Molecfit software in the observed spectrum of WASP-85Ab on the night of 2021 Feb 13 (T1) for single exposure. The observed spectrum is shown in blue line and the spectrum after telluric correction is shown in orange line. The dashed green vertical line represent the static position of atom spectral line at vacuum wavelength. Top panel: Telluric correction of spectral line around Na D1 & D2 lines. Bottom panel: Telluric correction of spectral line around the Hα lines.